digital power cables on preamps

Feel free to try any PC on any component.
Also, don't fall into the 'heavier gauge is better' trap. The type of gear, number of components, number of AC lines, and use of powerline filters can all affect the 'optimum' PC choice.
Audiogon is a great resource for trying PC's of different gauge and design. Buy a few PC's of differing specs, and hear what your particular system/components like best. You can always sell the ones that aren't synergistic with your gear.
Just MHO.

Calling it "digital" doesn't make it go faster :--) In the case of Signal and Element, they are just referring to the fact that those products are shielded (with both foil and braid, though braid alone is usually adequate.)

When used with digital equipment, a shielded power cord helps prevent the radiation of digital radio frequency (RF or 'digital hash') into the air. On non-digital equipment, shielding prevents the pickup of RF as well as EMI (electromagnetic interference, usually 60 cycle hum.)

For the shielding to be effective, it must be "floating." That means it's connected to the ground pin at only one end of the cord -- usually the AC plug end. (Note: UL regulations require OEM shielded cords to be connected to ground at BOTH ends. This is worse IMO than no shield, since it creates a ground loop and makes the cord MORE susceptable to hum pickup.)

Shielded power cords are always desireable, but mandatory on digital equipment.

As for conductor size, 10AWG is mandatory for amps (over 100W) and, for some weird reason, DACs or CDPs. 12 or 14 AWG is OK for most other stuff.

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